1. Field of the Invention
The present invention relates to a dynamic damper having a generally cylindrical shape, which is installed on a hollow or a solid rod member used as a vibration-transmitting member such as shafts, arms and conduits in various devices and being subject to oscillation or vibration, so that vibration of the rod member is reduced or absorbed.
2. Discussion of the Related Art
There are known various kinds of rod members such as shafts or arms functioning as a power-transmitting member and such as conduits or pipes serving as a fluid passage. Such a rod member generally tends to oscillate or vibrate and consequently suffers from problems of resonance thereof and undesirable transmission of the excited vibration therein to the other components of a device in which the rod member is used. As a method to cope with these problems, a dynamic damper is attached to the rod member. Examples of such a dynamic damper are disclosed in JP-A-2-190641, JP-B-6-37915 and JP-A-8-28627, wherein the dynamic damper has a metallic mass member having a generally cylindrical configuration and a pair of elastic support members formed on axially opposite sides of the mass member so as to extend axially outward directions, respectively. The disclosed dynamic damper is inserted onto the rod member and secured thereto at the elastic support members so that the mass member is elastically supported on the oscillating rod member via the elastic support members. Such a generally cylindrical dynamic damper is properly tuned so that the dynamic damper is capable of exhibiting effective damping characteristics with respect to a torsional or a circumferential vibration as well as a radial vibration of the rod member. Further, the mass member of the dynamic damper is less likely to drop off or released from the rod member, owing to its cylindrical shape, even if the elastic support member is undesirably broken. For these advantages, the dynamic damper has been used as a dynamic damper for a drive shaft of an automotive vehicle.
Such a conventional dynamic damper is installed onto the rod member such that the dynamic damper is disposed radially outwardly of the rod member. Therefore, the conventional dynamic damper is likely to interfere with other components disposed in the vicinity of the drive shaft, resulting in a limitation of the space for accommodating the dynamic damper. That is, the cylindrical dynamic damper is required to be made compact in its outside diameter.
Meanwhile, the cylindrical dynamic damper needs to have a sufficiently large mass of the metallic mass member, in order to effectively exhibit a desired vibration damping effect thereof. If the dynamic damper is made compact in size, however, the metallic mass member is accordingly made small in size, leading to difficulty in obtaining the desired mass of the metallic mass member. This results in deterioration of the vibration damping effect of the dynamic damper. Thus, the conventional dynamic damper has difficulty in meeting this downsizing requirement, sufficiently.